(a) Field of the Invention
The present invention relates to a resource allocation method of a base station. More particularly, it relates to a downlink/uplink scheduling and resource allocation method of a base station using space division multiplexing (SDM) with multiple antennas.
(b) Description of the Related Art
In a communication system, for example in an IEEE 802.16-based orthogonal frequency division multiplexing access (OFDMA) communication system, a base station may use multiple antennas and a terminal may use one or more antennas. In this case, the same radio resource that is defined by frequency and time can be allocated to a plurality of terminals. When the same radio resource is allocated to the plurality of terminals for data communication, the base station spatially divides the plurality of terminals by applying a proper antenna weight to each of the respective antennas so as to transmit/receive a signal with the plurality of terminals.
Spectrum efficiency can be improved by applying space division multiple access (SDMA) to the communication system, and therefore the base station performs scheduling and resource allocation through a process that requires a lot of calculation and time.
Particularly, the base station acquires radio channel information between the base station and a terminal to be served. Subsequently, the base station searches for a group of terminals that use the same radio resources and can be spatially divided, and at the same time, the base station selects an optimal radio resource and an optimal amount of radio resources that can be used by the group. In addition, the base station selects a proper modulation and coding scheme (MCS) for each terminal. Since the base station allocates radio resources through the above-described process, it is difficult to apply the SDMA when the length of a transmission frame is as short as 5 ms. In addition, service priority of each terminal must be considered when allocating the radio resources.
Further, the base station must allocate radio resources before a substantially allocated packet is transmitted, and therefore the base station cannot know a signal to interference-and-noise ratio (SINR) when the substantial packet is received. Therefore, the base station cannot determine a proper MCS for each service.